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61.
The stock of the European eel (Anguilla anguilla L.) continues to decline and has reached a new minimum in 2011. Poor health status of the spawners due to organic contaminants is one of the possible causes for this dramatic situation. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants, which are rapidly metabolized in vertebrates. EROD (ethoxyresorufin-O-deethylase) and GST (glutathione-S-transferase) are two enzymes involved in PAH detoxification in fish. In this study, PAH metabolites as well as EROD and GST activity in a large, comprising dataset of more than 260 migratory and pre-migratory eels from five large German river basin districts were used to describe PAH exposure and its metabolism as possible indicators for the habitat quality for eels. Eel from the river Elbe appear to be moderately contaminated with PAH. Highest mean values of PAH metabolites were analysed in fish from the river Rhine. However, the results suggest that contaminants such as PAH are metabolized in the fish and may have contributed to EROD activity in eels caught from the Elbe estuary to 600 km upstream. Since the eel’s onset of cessation of feeding is closely linked to maturation and migration, we propose bile pigments as new indicators contributing to identify the proportion of migratory eel, which is crucial information for eel management plans. We showed that PAH metabolites normalized to bile pigments as well as EROD could be used to describe the habitat quality and might be suitable parameters in search for suitable stocking habitats.  相似文献   
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In four different agricultural soils the long-term leaching behaviour of [14C]isoproturon was studied in outdoor lysimeters (2 m length, 1 m2 surface area). The herbicide was applied in spring 1997 and spring 2001. At the end of the first 4-year-investigation period between 0.13% and 0.31% of the applied radioactivity was leached. Isoproturon or known metabolites could not be detected in the leachate. However, shortly after the second application isoproturon and its degradation products 2-hydroxy-isoproturon and monodemethyl-isoproturon were leached via preferential flow in one of the lysimeters (Mollic gleysol) in concentrations of 4.5 microg L-1, 3.1 microg L-1 and 0.9 microg L-1, respectively, thus considerably exceeding the EU threshold limit of 0.1 microg L-1 for ground and drinking water. The results indicate that in soils where mass flow transfer dominates, leaching of isoproturon to groundwater is of low probability whereas in highly structured soils which have the tendency to form macropores, isoproturon can be transported via preferential flow to the groundwater.  相似文献   
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Pelagic, coupled ocean circulation-ecosystem models, are widely used in climate research. These tools aim to quantify fluxes of nutrients and carbon in the ocean and are, increasingly, the base of future projections. For this purpose it is crucial to quantify and identify the sources of uncertainties. In contrast to physical models, the underlying equations for ecosystem models are derived from empirical relationships rather than based on first principles. This resulted in the development of a multitude of different ecosystem models - different in respect to both, underlying principles and complexity. Clearly, the question arises, to what extent the sensitivities of these models are comparable.This study focuses on the intrinsic dynamics of some widely used, simple (containing 2-3 prognostic variables) ecosystem models in a 0-D framework (i.e., comprising only the well-mixed oceanic surface layer). A suite of differing model approaches is tuned such that their behavior is similar. The setup resembles the well-mixed oceanic surface layer in the Baltic proper. It is illustrated that strong differences between the model approaches appear due to exemplary, anticipated changes in the external nutrient and light conditions. Herewith, we demonstrate the well-known, but rarely demonstrated fact that, apparent consistency between modeled prognostic variables with today's data bases is not necessarily a good measure of forecast skill. The causes which lead to the different sensitivities are illustrated by considering the steady state solutions. It is pointed out, that apparently small changes in the model formulations can result in very different dynamical behavior and an enormous spread between the model approaches, despite the feasibility to tune a common behavior in a limited range of light and nutrient supply. In our examples, the sensitivity is mainly a function of the formulation of the loss rate of phytoplankton. It is thus, in particular, the formulation of highly unknown heteorotrophic processes that determines the model sensitivity.  相似文献   
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Purpose

The 'step-by step' principle was introduced into the European Union legislation on genetically modified organisms as a means to cope with uncertainty about environmental risks from the release of genetically modified organisms into the environment. The approval process is orientated along the stepwise reduction of containment which reflects a precautionary approach towards the risks of genetically modified organism release. Thus, the gradual reduction of containment should keep pace with the gradual generation of risk-related knowledge. This paper strives to clarify the meaning, legal status and practical importance of the principle. It also looks at whether non-European Union countries have adopted the principle as well, and how they practice it.

Methods

The article is based on research of the relevant legal texts, court cases and legal literature. In addition, a number of dossiers of applications for the European Union authorisation of release and placing on the market of genetically modified seed were analysed.

Results and conclusions

Although 'step-by-step' is not a precise legal rule it does have legal meaning as a principle guiding the risk assessment and management of genetically modified organism introduction into the environment. Assuming a process of gradual reduction of containment and scaling up of release ranging from closed systems via experimental release to cultivation the 'step-by-step principle' requires that the knowledge on environmental risks of genetically modified organisms should be generated on stages previous to the ones where the risk can result in damage. The analysis of the legislation of China, the United States of America and Brazil showed a differentiated approach towards the step-by-step principle.  相似文献   
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Within a Federal Environmental Agency research project to develop a biological test for hormone-mimetic compounds using the freshwater snail Marisa cornuarietis, the effects of the suspected xenoestrogenic substance bisphenol A (BPA), not only on freshwater but also on marine prosobranch snails, were investigated. For the laboratory experiments the ramshorn snail Marisa cornuarietis and the ovoviviparous snail Potamopyrgus antipodarum were considered as freshwater species and two marine prosobranchs, the netted whelk Nassarius reticulatus and the dog whelk Nucella lapillus, were additionally employed. N. reticulatus, as a typical sediment-living species, was exposed via artificial sediments, while the three other prosobranchs were exposed via water. The test series with Marisa cornuarietis covered a nominal concentration range between 1 and 100 μg BPA/l in a 5 month experiment with adult snails and a complete life cycle test for 12 months. Additionally, a third test in the nominal range between 0.05 and 1 μg BPA/l (measured: 0.0079–0.404 μg/l) was performed with adults snails for 6 months. In these experiments, BPA induced a complex syndrome of physiological and morphological alterations in female Marisa referred to as the induction of ‘superfemales’. Affected specimens were characterised by the formation of additional female organs, an enlargement of the accessory pallial sex glands, gross malformations of the pallial oviduct section resulting in an increased female mortality, and a massive stimulation of oocyte and spawning mass production. For these tests, an LOEC of 48.3 ng/l, an NOEC of 7.9 ng/l and an EC10 of 13.9 ng/l were calculated. Superfemales occurred also in the BPA exposure experiment with the other snail species, but comparable oviduct malformations as in Marisa were not found, probably due to species differences in the gross anatomical structure of the pallial oviduct. During the 9 week test with Potamopyrgus antipodarum in the nominal concentration range between 1 and 100 μg/l, BPA induced an enhancement of embryo production even in the sexual repose phase of the reproductive cycle. A characteristic inverted U-type concentration response relationship was found. Nassarius reticulatus was exposed via BPA-spiked artificial sediments (nominal concentration range: 10–1000 μg/kg dry wt.) for 3 months. BPA exhibited a significant and concentration dependent uterotrophic effect which could be detected not only by an enlargement but also by a weight increase of the accessory pallial gland complex in the pallial oviduct section. Adult Nucella lapillus were tested for three months in the laboratory in a nominal concentration range between 1 and 100 μg BPA/l. Superfemales in the dog whelk were also characterised by enlarged accessory pallial sex glands and an enhancement of egg production, but the test compound also affected the males in this species. A lower percentage of exposed specimens had ripe sperm stored in their vesicula seminalis and male Nucella exhibited a reduced length of penis and prostate gland when compared to the control. Because statistically significant effects were observed already at the lowest nominal test concentration (1 μg/l), it can be assumed that even lower concentrations may have a negative impact on the snails. The results show that prosobranch snails are affected by BPA at lower concentrations compared to other systematic taxa in the animal kingdom. Consequently, it has to be claimed that the results of these experiment have to be considered for the current EU risk assessment for BPA in order to achieve a sufficient protection of wildlife in aquatic ecosystems.  相似文献   
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Regional Environmental Change - Land use and spatial patterns which reflect social-ecological legacies control ecosystem service (ES) supply. Yet, temporal changes in ES bundles associated with...  相似文献   
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